1. Field of the Present Invention
The present invention relates to a container that has excellent gas barrier properties against, for example: oxygen and carbon dioxide; moisture-proofing properties; flavor-retention properties; flavor-barrier properties; and impact delamination resistance. In addition, the container of the present invention has a good appearance and can be stably produced in long-run working lines.
2. Discussion of the Background
Thermoplastic polyester (hereinafter abbreviated as PES) containers that have been obtained through stretch blow molding have gained popularity and are employed in several fields. The reason for their notoriety can be assigned to their various excellent properties, such as transparency, mechanical superiority and flavor barrier properties. In addition, the moldings of stretch blow molded PES containers are almost free from the risk of releasing residual monomers and harmful additives. Accordingly, these containers generally have excellent sanitation and safety records.
A particularly popular PES containers are multi-layer containers that employ a combination of PES and ethylene-vinyl alcohol copolymer (hereinafter abbreviated as EVOH), due to the good gas barrier properties. The use of these multi-layer containers are expected to be expanded to containers for drinks, foods, cosmetics, etc., since they can be produced in a simple apparatus and have good appearances. In addition these containers have the beneficial properties of both individual components: PES and EVOH. However, the aforementioned multi-layer containers are not free of problems. The critical problems associated with these ordinary multi-layer containers include: poor point-of-impact delamination resistance and poor transparency.
Among the proposals to address the problems associated with multi-layer containers, JP-A 11-348194 sets forth multi-layer containers comprising PES and partially-saponified EVOH that are produced through coinjection stretch blow molding. JP-A 11-348194 states that these multi-layer containers have good impact delamination resistance and transparency. The multi-layer containers are epoch-making ones in that they have satisfactory impact delamination resistance though not having adhesive resin between PES and EVOH. However, these multi-layer containers have some problem associated with gas barrier properties and thermal stability since they comprise partially-saponified EVOH. To solve this problem, other multi-layer containers have been proposed, which comprise an EVOH mixture of two different types of EVOH having different melting points (JP-A 2001-277341). These multi-layer containers have good impact delamination resistance and transparency and have improved gas barrier property and thermal stability. However, partially-saponified EVOH is still an indispensable component in the multi-layer containers, particularly in the production of the multi-layer containers in long-run working lines, and its thermal stability is not a negligible matter.
Accordingly, there remains a critical need for a multi-layer container that has excellent gas barrier properties, moisture-proofing properties, flavor-retention properties, flavor-barrier properties, and impact delamination resistance, which has a good appearance and can be stably produced in long-run working lines.